Stronger Intermolecular forces (greater attractions) hold molecules together better. Meaning the molecules don't want to leave whatever liquid they are part of. for example, chloroform(the knock out gas), which has only weak intermolecular forces evaporates very quickly at room temp.
However, water which participates in H-bonding, strong intermolecular forces, evaporates slowly at room temp.
The colder a liquid is, the harder it is for the molecules to overcome their intermolecular bonds and break free. a.k.a. slow evaporation. but when a liquid is heated the molecules have enough energy to overcome their brotherly bonds and go into the gas phase.
